Per Mertesacker is entrusted with the job of collecting fines from Arsenal players in breach of club discipline but the German may find himself going cap in hand to manager Arsene Wenger for his place in the team.

Kevin Pietersen is returning home immediately from New Zealand because of a knee injury and could be a doubt for this summer’s Ashes showdown.

The setback will keep him out of action for at least six weeks and an official statement from the England and Wales Cricket Board said he will miss the final Test of the series against the Kiwis plus his lucrative season in the Indian Premier League.

The ECB have conceded his place in the home series against New Zealand, which starts in mid-May, is in severe doubt. After that they can only hope Pietersen responds to treatment for the Champions Trophy in June and the flagship series against Australia, which begins in July.

Pietersen’s injury first arose during fielding practice before England’s warm-up match in Queenstown three weeks ago, since when he has played two Tests. According to a statement from the ECB issued late at night in New Zealand, the pain “has failed to resolve satisfactorily”.

Scans have confirmed bone bruising and possible cartilage damage. Pietersen will leave for home as soon as possible for a specialist review in England. Early indications suggest that it will require rest and rehabilitation for between six and eight weeks.

Questions are bound to be asked about why Pietersen, 32, was allowed to play in two Test matches after first feeling discomfort. His practice sessions lately have been noticeable for the brace he has worn around his knee, although his movement does not seem, to the untrained eye, to have been restricted.

After a quiet first Test, Pietersen batted for three-and-a-half hours in England’s only innings in the Second Test at Wellington last week in making 73. While he was far from fluent he did not seem to be in any discomfort.

England will now be desperate to ensure he is fit for the Ashes series at home this summer. Although they managed to beat Australia at home in 2009 largely without him — he had an Achilles injury on that occasion which came close to ending his career — they would not especially care to try it again.

But at the back of everybody’s minds will be the fact that it was a debilitating knee injury which ended the career of another England batsman of recent times, Michael Vaughan.

Pietersen is the second England player to fly out early from the New Zealand tour after an elbow injury forced spinner Graeme Swann home.

Swann, 33, also aggravated his long-standing problem during the match at Queenstown and underwent successful surgery in the United States last week. The off-spinner is expected to return in time for the Champions Trophy in June.

Pietersen has been an aloof figure on this tour, at least as far as the press is concerned. He has fulfilled none of the routine media duties that are expected of the modern player although his relations with the team seem as cordial as they have been for years.

It was only seven months ago that Pietersen was dropped by England after apparently falling out with most members of the dressing room.

He was accused of sending disparaging texts about Andrew Strauss, the captain at the time, to members of the South African team. Pietersen was eventually recalled to the side for the tour of India last year.

He played one of the greatest of all innings in Mumbai — scoring 186 — to help England win the Second Test.

It has become clear since then that England would like to airbrush from history the whole Blackberry incident. When Pietersen eventually made a kind of peace with the management it was said that he would need to become “rehabilitated”.

As far as anyone knows that has been done. The players who were once against him now appear more than tolerant of him.

England would have preferred this injury not to happen but Pietersen, as he has demonstrated so often whether advertently or not, will always find a way to be in the headlines.